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not too long ago I purchase 3 of the receivers in the subject line. Up till now I worked with the 623's but those are discontinued.

I soldered the receiver in my circuit - and supprize - it doesn't work. I mean it works - for 8 secconds then 8 seconds off. Then it comes on again, and 8 seconds later the picture disappears.

I thought this is a bad receiver. So I took the second one - doing the same thing... So I try the third one - this is the same as well...

This circuit is a new design, the receiver is soldered into it's own pcb with a connector which plugs into the baseboard. the baseboard contains the power regulator, the dip switch, the connectors, etc.

The only thing I did differently compared to the circuit I used the 623's in, that I added the reccomanded capacitors on the Video and the two audio outputs. My previous receivers didn't have that.

The regulator has 2 capacitors SMT 0.01 and 0.22uf.

All the traces are correct, no short circuit - I am stunned, I though I first ask you guys before I send it back to the provider.

(1) The LM2940 is dissipating about 1.5 watts. To avoid thermal shutdown, it must be bolted to your PCB. It may require additional heat-sinking.

(2) The stability caps on the Vreg are too small (are any really installed?). For example, the .22uF on the output might not prevent oscillation, which will cause very strange results. Please check the LM2940T-5.0 data sheet.

(3) The DIP switch appears to be set to an illegal channel.

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I'm for the DIP switch problem. Some modules, if more than one channel is selected, will switch between all the selected channels every few seconds. On your photo there are 3 DIPs set to ON. I can't see easily how you wired them, but on the module you have 3 inputs, if all of them are open or high channel 4 is selected, and each of them will allow to select channels 1,2 and 3 when grounded, but only one at a time.

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It was the dip switch problem. I hate these when they do not mark it clearly which way is on, which way is off... On this one there is a line and it says "Open"...

On the test board I do have the LM2940T bolted to the board, and the caps are installed on the bottom - on these pictures were not yet on. The LM2940 is barely heating up, so I don't think it will need a heat sink. I will run it for a longer period to see if there is any heat problem.